According to an electric power steering device, which assists a steering force using an electric motor, an assist force is generally determined based on a steering torque detected by a torque sensor, so as to drive and control the electric motor.
For example, Patent Document 1 discloses a technology for detecting a failure of the electric power steering device. According to this technology, a control means for conducting motor control is monitored using a failure detection means, and a failure detected by the failure detection means is stored in a failure memory means. This allows appropriate failure analysis, because all necessary failure information is stored without omission.